1. Field of the Invention
The invention relates to a novel solid-state battery electrode and to a method of producing this electrode. The invention more particularly relates to a solid-state battery electrode that is formed of a lithium ion conductor, an active material, and a solid electrolyte each having a special structure and thereby can provide a high output when used in a solid-state battery, and to a method of producing this solid-state battery electrode.
2. Description of Related Art
Lithium batteries have entered into practical use in recent years as high voltage and high energy density batteries. Various investigations are underway in pursuit of additional improvements in lithium battery performance due to demands for higher performance levels and the desire to increase the application of lithium batteries into a broader range of fields. Among these investigations, there is desire for the realization of practical solid lithium batteries since they could offer many advantages over the heretofore used nonaqueous electrolyte-based lithium batteries, i.e., better safety, greater structural flexibility due to greater flexibility with regard to cell shape, and a reduction in auxiliary components.
However, such a solid lithium battery has remained unrealized to date. In order to obtain a solid lithium battery that can exhibit the characteristic features noted above, each of the electrodes, i.e., the positive electrode and the negative electrode, and the solid electrolyte must all be constructed of materials that can provide safety in combination with a high output. However, electrodes that can provide a high output and/or a solid electrolyte that can provide a high output have not yet been obtained.
With regard to electrodes, there have been investigations into electrodes for nonaqueous electrolyte-based lithium batteries and electrodes for solid-state lithium batteries. For example, Japanese Patent Application Publication No. 5-290849 (JP-A-5-290849) describes a positive electrode for a nonaqueous electrolyte-based secondary battery. This positive electrode uses a positive electrode active material that has a large particle diameter and is obtained by mixing, granulating, and baking starting inorganic compound powders. As a specific example here, the example is given of the production of LiCoO2, which is one example of a positive electrode active material, by subjecting a mixture of lithium carbonate and cobalt oxide to stirring, mixing, and granulation.
In addition, Japanese Patent Application Publication No. 2008-004459 (JP-A-2008-004459) describes a sulfide electrolyte particle that has an average particle diameter of 0.1 to 10 μm and that can lower the solid electrolyte/electrode interfacial resistance. This sulfide electrolyte particle is obtained by subjecting a sulfide solid electrolyte particle to multistage milling in a nonaqueous vehicle or to dry milling using a jet mill. However, JP-A-2008-004459 does not provide a specific example in which a positive battery electrode is obtained from the sulfide electrolyte particle, a conductor, and an active material and also makes no reference to battery output.
Thus, while the related art has a positive electrode active material particle obtained by mixing, granulation, and baking and an electrolyte particle obtained by dry milling, it is quite difficult using these conventional materials to obtain a solid-state battery electrode that can provide a high output.